Method of electrically braking alternating-current motors.



No. 851,891. PATENTED APR. 30, 1907.

W. A. LAYMAN. METHOD OF ELBGTRIGALLY BRAKING ALTERNATING CURRENT MOTORS.

APPLIGATION FILED AUG. 6, 1906.

3 BHEETSBBBB'X 1.

WITNESSES. lNVEA/TOR z? W. A. Layman.

ATTORNEYS PATENTED APR. 30, 1907.

W. A. LAYMAN. METHOD OF ELEOTRIGALLY BRAKING ALTERNATING CURRENT MOTORS.

APPLICATION FILED AUG. 6, 1906.

3 SHEETS-SHEET 2.

mmvnm W. A. Layman.

ATTORNEYS PATENTED APR. 30, 1907.

W. A. LAYMAN. I METHOD OF ELEOTRIGALLY BRAKING ALTERNATING CURRENTMOTORS.

APPLICATION FILED AUG. 6, 1906.

3 SHEBTS-SHEET 3.

Fig.3.

lIV VE N 70/? W. A. Layman.

Arromvfy WALDO A. LAYMAN, OF ST. LOUIS, MISSOURI. METHOD OF ELECTRlCALLYBRAKING ALTERNATlNG-CURRENT MOTORS.

Specification of Letters Patent.

Patented April 30, 1907.

Application filed August 6, 1906- Berlal No. 829,352.

city of St. Louis, in the State of Missouri,

have-invented a certain new and useful Method of Electrically BrakingAlternating- Current Motors, of which the following is such a full;clear, and exact description as will enable any one skilled in the artto which it appertains to make and use the same, reference being had tothe accompanying drawings, forming part of this specification.

' Heretofore alternating current motors have been at a disadvantagerelative to direct current motors in work requiring efficient brakingmeans, because an alternating cur rent motor cannot be inherentlychanged like the direct current motor from a motor to a generator inorder to provide braking means. To overcome this difficulty l rovide anauxiliary current either generated by the rotation of the motor orderived from an independent source and controlled by the rotationof' themotor, and utilize such auxiliary current to oppose the rotation of themotor. In the preierred manner of carrying out my invention, I utilizesuch auxiliary current by introducing it into the motor to establishthereby a torque opposed'to the momentum or'inertia torque of the motor.I may, however, utilize such auxiliary current by means of a magneticbrake. My method is especially adapted for use in connection with motorsfor elevators, as in such work efficient and reliable braking means arees ecially desirable.

.n the accompanying drawings which illustrate some forms of ap aratusadapted to carry out my invention, *igure .1 is a iagram illustrating aparatus in which an auxiliary direct current is introduced into the motorto eiiect the braking. Fig. 2 is a diagram illustrating apparatusinwhich an auxiliary alternating current is introduced into the motor, andFig. 3 is a diagrammatic view illustrating apparatus in which theauxiliary current opposes the rotation of the niotor bymeans of amagnetic brake. I

Like marks of reference refer to similar parts in the several views ofthe drawings.

I 5 represents the armature or rotor of the known types of alternatingcurrent motors. In the type shown the windings of the armature or rotor5 are connected to a commutator 7 provided with brushes 8 connected byresistance 9 so as to establish a definite line of polarity in thearmature. The winding of the armature 5 is also provided with apolyphase circuit 10 containing resistances 11 adapted to be cut into orout of the circuit by means oi a rotary contact member 12. The currentis adapted to be led through the windings oi the field 6 by means oiconductors 15 and 15 so as to rotate the armature 5 in one direction, orthe current may be led through the said field by means of conductors 16and 16 to rotate the armature 5 in the opposite direction. The currentfor driving the motor is derived from mains i7 and 18 and is controlledby a switch mechan-.

ism now tobe described.

Referring now to Fig. 1, the conductor 15 leads to an annular contactring 19. This contact ring 19 is divided so-as to form segments 2-0 and21, the conductor 15 being connected to the segment 20. The conductor 16'hereinbefore referred to is connected with the segment 21. A secondcontact ring 19 is also provided adjacent to the ring 19 and divided toform segments 20 and 21. The segment 20 is connected with the conductor15 and the segment 21 with the conductor 16. Adjacent to the contactring 19 are contacts 22, 23, 24: and 25. Adjacent to the contact ring 19are similar contacts 22, 23, 24 and 25. These contacts are adapted to beconnected with the rings by means of switch arms 26 and 26. These switcharms 26 and 26 are connected by means of a link 27 so as to move inunison over the contact rings, and are adapted to move in the directionof the arrows in Fig. l. The contacts 22 and 24 are connected by meansof wires 28 with the line 18, While the contacts 22 and 24' areconnected by wires 29 with the main 17. The

contacts 25 and 23 are connected together- 7", I, the

. mature. After passing through the field the current returns by meansof the conductor 15,- seg'ment20, switch arm 26-and wire 28 to the linewire 18, thus completing the circuit to through the motor and causing itto rotate in one direction. If, now, the switch arms 26 and 26 be movedin the direction of the arrow so as to bring said arms in engagement.

with'the contacts 23 and 23, the current rfrom the line wires will becut on from the motor and at the same time the small genera- .tor 31'will be thrown into circuit to supply an auxiliary current to the motor.Said auxiliary current passes from the conductor '20 30 through contacts25 and 23 to the swltch arm 26 and thence throlilgh the segment 20' andconductor to the old 6. Thereturn circuit from the field 6 is madethrough the conductor 15, segment and switch arm 26 1 .to the contact 23and thence through the conductor 32 to thegenerator 31, thus completingthe circuit. The auxiliary current thus introduced into the fieldfiofthe motor will create inthe said motor a torque opo posed to the inertiaor momentum torque of thev motor and will consequently brake the 'motor.The said current being enerated from the rotation of the motor, l-beproportional to the speedof the motor, and, con- 5" sequently will applythe maximum brakmg force when the motor is running at the highest s eed,and a less braking force as the motor. ecreases its speed. A continuedmovement of the arms 26 and.2.6 will cause the d motorfirstto run in theopposite direction when thefarms are on contacts 24 and 24 and again tobrake the motorwhen the said arms are on the contacts 25 and 25'.

Referringnow to-Fi 2,, an apparatus is 45' shown wherein the auxi iarycurrent is an alternating current derived from the mains.

The motor shown in this figure is'in all res cts' the same as that showninFig. 1 and th switch mechanism is the same except 5o that the sectors'20 and 21 and 20 and 21 are rotated relatively to the contacts so thatwhen the'swjtcharms26 are-on the contacts 22 or 25 they. willbe on thesectors 20, and when on the contacts 23 or 24 they will be on 5 5'the'sectors'21; In the arrangement hereinv before describediii-connection with Fig.- 1,

thesector's areso arranged that the arms-26' connect the contacts '22and 23 with the sectors. 20, and the contacts 24 and 2.5 with the 6osectors 21; The object of this change in the switching mecpam'sm in theapparatus shown cad-the auxilia current into I ldifi'by conductors atright angles to those carrying the operating current immedi- 6 5 atelybefore the auxiliary current is .intro.

; duced into the motor. 1 In the apparatus shown in Fig. 2 the wires 30and 32 in place to a generator lead'to the secondof leading ary 37 o atransform'er, the primary 38 of which is connectedacross the mains 17-and 18. The secondary 37 of the transformer is divided into sectionsconnected to contacts 39, one of which is also connected with the wire30. The wire 32 is connected to the sector 40 adjacent to the'contacts39 and adapt& .15 I a ed to-be connected therewith by means 0 ivoted arm41; This arm 41 is connected g y means of the system of levers A2 with acentrifugal "governing device 43 which is driven from the motor by meansof the belt 33 hereinbefore described, the pulley. 35 driven by suchbelt being geared to the said governor 43. This governor'isso arrangedthat when the motor is at speed the arm will be in the position shown inthe drawings, so as tocut' the entire secondary of the transformer inthe circuit. When, however, the speed of the motor decreases, the arm 41will be moved in the direction of the arrow inthe drawings so as toadually'cut the transformer out of circuit, until when the motor is atrest the entire secondary of the tr'ans- .former will be cut out. i

Inthe o eration of the device shown in Fig. 2,.the, iving1 current iscarried through the motor when t e parts are in the position shown inthe h re by circuits similar to those first descri ed in connection withapparatus in Fig. 1. 26 and 26 are moved on to the contacts 23 and23,the auxiliary current from the transformer secondary 37 will passoverthe line 30 through the contacts 25 and 23 to the arm 26and thencethrough the conductor 16 to the field 6. The return circuit is throughthe. conductor 16, and thence through the sector 21 and arm 26 to thecontact 23 and through the conductor 32 back to the transformer. It willthus be seen that the auxiliary current is introduced into the motorthrough the conductor '16 andlfi" at right an les to the conductors 15and 15 from whlchthe main driving current has beencut off. This currentwhen so ap lied produces in the motor a torque o pose to the inertia ormomentum torque oi. the motor and thus brings it to rest. As the speedof the motor decreases the centrifugal governor 43 will cause the arm 41to move-in the direction of the arrow so as to gradually cut'thesecondary of the transformer out of circuit and thus regulate "theauxiliary current so that it is proportional to the speed of the 'motor,and when themotor has come to rest the secondary will be entirely outout-so that no loss of energy will take place in the transformer whilethe'motoris at rest. I

In the apparatusshown in' Fig. 3 the arrangement of parts are the sameas that .loo

When, however, the arms after to be described.

A tional'parts 45 and 46 and 45 wire to the contact 23 the arm 26 andsector 45' motor, is proportional to the speed'of the mocurrent motor,

.and 26 aremoved in the The contact rings 19 and 19 of this apparatusare each divided into four sectors inplace of two, the addiand 46 beingconnected to a magnetic brake 47 placed adjacent to a disk 48 on ture 5.One wire 49 leading from said magnetic brake is connected to the sectors45 and. 46, and the otherline 50 is connected to the sectors 46 and 45.

In the operation of the apparatus shown in Fig. 3, when. the parts arein the position shown in the figure the current will pass through themotor by circuits like those de scribed in connection with the apparatusin Figs. 1 and 2. When, however, the arms 26 direction of the arrow-soas to bring said arms in engagement with the contacts 23 and 23, thecurrent from the generator 31 will pass through the and thence throughto the conductor 50 leading to the magnetic brake 47. The currentreturns from the said brake 47 throu h the conductor 49 to the sector 45and t ence through the arm 26 and line '32 it returns to the generator31, completing the circuit. The action of the brake 47 is to draw thedisk 48 against it so that the friction between the two parts opposesthe-rotation of the motor and brings it to rest. The current energizingthe brake 47, being furnished bythev generator 31 driven from the tor,thus furnishing braking power of greater or less amount, according asthe motor is rotating with greater or less speed.

Having fully described my invention, what I claim as new and desire tosecure by Letters Patent of the United States, is

l. The method of braking an alternating current motor, which consists,after the main driving current has been cut off from the motor, invarying an auxiliary current with the speed of the motor, and applyingsaid auxiliary current to oppose the rotation of the motor.

2. The method of'braking an alternating current motor, which consists,after the main driving currenthas been cut off from the motor, ingenerating an auxiliary current by the rotation f the motor, and aplying Said auxiliary current to oppose-t e rotation of the motor.

3. The met-hod'of braking an alternating which consists in introducingthe shaft of the arma-' rent hasbeen cut off into the motor, after themain driving current has been cut off from the motor, an auxiliarycurrent, and reorganizing the windings to establish thereby a torqueopposed to the inertia or momentum torque of the motor;

4. The method of braking an alternating current motor, which consists inintroducing into the motor, after the main driving current has been cutoil" from the motor, an auxiliary direct current, and reorganizing thewindings to establish'thereby a torque opposed to the inertiaor-momentum torque of the motor.

5. The method of braking an alternating current motor, which consists inintroducing into the motor, after the main driving current has been cutoil from the motor, an

auxiliary currentvarying with the speed of the motor, and reorganizingthe windings to establish thereby a torque opposed to the inertia ormomentum torque of the motor.

.6. The method of braking an alternating current motor, which consistsin introducing into the motor, after the main driving current has beencut off from the motor, an auxiliary current generated by the rotationto establish thereby a torque opposed to the inertia or momentum torqueoi the motor.

7. The method of braking an alternating current motor, which consists inintroducing into the motor, after the main driving current has been cutoil from the motor, an auxiliary direct current varying with the speedof the motor, 5 and reorganizing the windings to establish thereby atorque opposed to the inertia or momentum torque of the motor.

8. 'The method of braking an alternating current motor, which consistsin introducing into the motor, after the main driving curfrom the motor,an auxiliary direct current generated by the rotation of the motor, andreorganizing the windings to establish thereby a torque opposed to theinertia or momentum torque of the motor.

In testimony whereof, I have hereunto set my hand and affixed my seal inthe presence of the two subscribing witnesses.

WALDO A. LAYMAN, a. 5.1

of the motor, and reorganizing the windings

